71449-74-6Relevant academic research and scientific papers
Effect of ortho-SR groups on O-H bond strength and H-atom donating ability of phenols: A possible role for the tyr-cys link in galactose oxidase active site?
Amorati, Riccardo,Catarzi, Francesca,Menichetti, Stefano,Pedulli, Gian Franco,Viglianisi, Caterina
, p. 237 - 244 (2008/09/21)
Rotation about the Ar-S bond in ortho-(alkylthio)phenols strongly affects the bond dissociation enthalpy (BDE) and the reactivity of the OH group. Newly synthesized sulfur containing heterocycles 3 and 4, where the -SR group is almost coplanar with the phenolic ring, are characterized by unusually low BDE(O-H) values (79.6 and 79.2 kcal/mol, respectively) and by much higher reactivities toward peroxyl radicals than the ortho-methylthio derivative 1 (82.0 kcal/mol). The importance of the intramolecular hydrogen bond (IHB) in determining the BDE(O-H) was demonstrated by FT-IR experiments, which showed that in heterocycles 3 and 4 the IHB between the phenolic OH group and the S atom is much weaker than that present in 1. Since the IHB can be formed only if the -SR group adopts an out-of-plane geometry, this interaction is possible only in the methylthio derivative 1 and not in 3 and 4. The additive contribution to the phenolic BDE(O-H) of the -SR substituent therefore varies from -3.1 to +2.8 kcal/mol for the in-plane and out-of-plane conformations, respectively. These results may be relevant to understanding the role of the tyrosine-cysteine link in the active site of galactose oxidase, an important enzyme that catalyzes the two-electron aerobic oxidation of primary alcohols to aldehydes. The switching of the ortho -SR substituent between perpendicular and planar conformations may account for the catalytic efficiency of this enzyme.
Thermal Claisen Rearrangement Studies on 4,6- and 2,4-Diacetylresorcinol Bisallyl Ethers: Observation of Loss or Sigmatropic Shift of Acetyl Groups
Anjaneyulu, Ammanamanchi S. R.,Mallavadhani, Uppuluri V.
, p. 623 - 628 (2007/10/02)
Thermal Claisen rearrangement of 4,6-diacetylresorcinol bisallyl ether (2) in N,N-dimethylaniline gave a mixture of readily characterised products.While no rearrangement occurred with lower boiling solvents (benzene and dioxane), higher boiling solvents (diphenyl ether and glycerol) gave rise to more complex rearrangement and a lowering of the yields of isolable products.Trifluoroacetic acid both at room temperature and 60 deg C effected either partial or total deallylation but no rearrangement.Product formation has been rationalised in terms of symmetry allowed sigmatropic allyl, acetyl or H shifts followed by allyl or acetyl group loss; the latter is a novel obsrevation.The acetyl group, most probably eliminated as a cation, effected both O-acylation and nuclear acylation of the substrates.Claisen rearrangement of the bromo and nitro derivatives of compound (2) in which the ortho and para positions are blocked, gave products arising from bromo and nitro group elimination.Rearrangement of 2,4-diavetylresorcinol bisallyl ether N,N-dimethylaniline occurred similarly.
